arraylist removeall 28collection c 29 method in java

1import java.util.ArrayList;
2public class ArrayListRemoveAllExample
3{
4   public static void main(String[] args)
5   {
6      try
7      {
8         ArrayList<Integer> al1 = new ArrayList<Integer>();
9         al1.add(2);
10         al1.add(4);
11         al1.add(6);
12         al1.add(8);
13         al1.add(10);
14         System.out.println("ArrayList before using removeAll() method: " + al1);
15         // create another ArrayList
16         ArrayList<Integer> al2 = new ArrayList<Integer>();
17         al2.add(2);
18         al2.add(4);
19         al2.add(6);
20         // print al2
21         System.out.println("Elements to be removed: " + al2);
22         // remove elements from ArrayList using removeAll() method
23         al1.removeAll(al2);
24         // print al1
25         System.out.println("ArrayList after using removeAll() method: " + al1);
26      }
27      catch(NullPointerException ex)
28      {
29         System.out.println("Exception: " + ex);
30      }
31   }
32}